Transcript of "Mechanical ventilation in COPD Asthma drtrc"

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COPD <ul><li>It is defined as a preventable and treatable disease state characterized by airflow limitation that is not fully reversible </li></ul><ul><li>The airflow limitation is in most cases is both progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases . </li></ul><ul><li>Although COPD affects the lungs, it also produces significant systemic consequences </li></ul>

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Why COPD is Important ? <ul><li>COPD is the only chronic disease that is showing progressive upward trend in both mortality and morbidity </li></ul><ul><li>It is expected to be the third leading cause of death by 2020 </li></ul><ul><li>Approximately 14 million Indians are currently suffering form COPD* </li></ul><ul><li>Currently there are 94 million smokers in India </li></ul><ul><li>10 lacs Indians die in a year due to smoking related diseases </li></ul><ul><li>* The Indian J Chest Dis & Allied Sciences 2001; 43:139-47 </li></ul>

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In COPD limitation is EF <ul><li>No conventional ventilator supports expiration actively </li></ul><ul><li>How does MV help ? </li></ul><ul><li>Although the load is expiratory the failure is inspiratory </li></ul>Inspiratory muscle loading and fatigue is of central pathophysiological importance in the development of acute respiratory failure

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Concept of DH <ul><li>It is a adaptive mechanism which leads to increased elastic recoil force and keeps airways patent to force out air but…. </li></ul><ul><li>Due to use of accessory muscle usage increased force is also applied to airways which lead to collapse & exaggerate the EFL </li></ul>

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Concept of Auto PEEP, DH <ul><li>AUTO PEEP is defined as the difference between PEEP set by the clinician and the PEEP as measured by the ventilator with an expiratory hold. </li></ul>

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WHAT ARE EFFECTS OF AUTO PEEP? <ul><li>Hemodynamic compromise. </li></ul><ul><li>Due to increase in FRC, respiration starts in the flatter portion of the P/V curve, where change in volume for a change in pressure is less –Increased WOB. </li></ul><ul><li>Trigger will have to cross the auto PEEP level before inspiration is initiated. </li></ul><ul><li>Missed breaths </li></ul>

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Minute ventilation <ul><li>Tidal volume=6-7ml/kg </li></ul><ul><li>Rate 12/mt, IC is reduced </li></ul><ul><li>Low minute ventilation leads to ↑ PCO2 which is the price we pay for preventing DH, </li></ul><ul><li>In fact current literature suggests that risk of dynamic hyperinflation is much larger than those of permissive hypercapnia. </li></ul><ul><li>Provide enough ventilation to keep a normal PH, not a normal PCO2. </li></ul>

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Can PEEP be used in all COPD pts? <ul><li>Whenever accessory muscles are in use to counter act them PEEP can be used </li></ul><ul><li>when patients are on partial/ supported modes </li></ul><ul><li>In asthmatics and when patients are paralysed the response can be variable and unpredictable… </li></ul><ul><li>Then the question arises how to be sure it is not harmful? </li></ul>

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Ventilation difficulties in COPD <ul><li>Ventilating a COPD patient is difficult because the disease may not have a reversible component, </li></ul><ul><li>Quantifying dynamic hyper inflation at bedside is very difficult </li></ul><ul><li>COPD patients are difficult to wean. </li></ul><ul><li>Co morbidities & systemic effects </li></ul>

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Intubation and MV <ul><li>Decision to intubate if the patient is not a candidate for NIV or has not done well on NIV- has to be made decisively and if delayed both morbidity and mortality are higher. </li></ul><ul><li>Post intubation bagging has to be low tidal volume and low rate 6-7/mt. </li></ul>If paralysed keep them on relaxants for a day or two. Fill them adequately before induction , Add a small dose of a inotrope in a corpulmonale patient

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Ventilation in a passive patient <ul><li>External-PEEP application has a variable and unpredictable response </li></ul><ul><li>Due to no contribution of the expiratory muscles, the reason how external PEEP helps to reduce DH </li></ul><ul><li>Reducing the lung heterogeneity. </li></ul><ul><li>Opening up previously closed units it could help in mucus clearance and bronchodilator therapy. </li></ul>

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Ventilating a spontaneous patient <ul><li>You rarely require more than 10cmH2O PEEP. </li></ul><ul><li>Expiratory sensitivity (PS) can be set much above the default setting of 25%.( 40%) </li></ul><ul><li>If the patient is not synchronizing, increasing PS could lead to increased VT, DH, and missed breaths. </li></ul><ul><li>In such a situation other causes like fever, pain etc have to be looked for. In case no other cause can be found, sedation can be used . </li></ul>

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Weaning <ul><li>Weaning begins when the precipitating factor of the respiratory failure is partially or totally reversed. </li></ul><ul><li>Marginal respiratory mechanics. </li></ul><ul><li>Factors which increase resistance like size of the tube, deposition of secretions in the tube, kinking/curvature of the tube, presence of elbow-shaped parts, HME in the circuit </li></ul>Steroids + Relaxants Myopathy

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Weaning <ul><li>Role of tracheostmy is uncertain, but due to marginal respiratory mechanics it is thought it may help in weaning. </li></ul><ul><li>Weaning can be done with PS mode to SBT. </li></ul><ul><li>In very difficult cases extubation on to NIV is a option </li></ul><ul><li>Corpulmonale may warrant small dose of inotrope, a dose of diuretic & low fluid strategy during weaning. </li></ul>

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IN COPD <ul><li>Preventing VILI is not the primary objective here; </li></ul><ul><li>Avoiding barotrauma, improving airway clearance, and reducing the consequences of hyperinflation have been the motivators. </li></ul><ul><li>Yet, use of small VT for avoidance of high plateau pressure, </li></ul><ul><li>Acceptance of permissive hypercapnia, </li></ul><ul><li>Judicious use of PEEP to lessen effort and perhaps to reopen compromised airways in some patients now guide the care of obstructed patients as well. </li></ul>